Force sensors are sensors that detect forces and moments acting along at most six axes in a three-dimensional coordinate space with an X axis, a Y axis, and a Z axis, which are forces Fx, Fy, and Fz acting in translation directions along the individual axes and moments Mx, My, and Mz acting in rotation directions along the individual axes. Such a force sensor is mounted in, for example, a wrist portion of an industrial robot hand. The force sensor can detect forces and moments that are generated in an assembly task to obtain detected values, and can modify an operation of the assembly task in accordance with the detected values. Regarding a detection principal of a force sensor, a sensor utilizing a magnetic detection method as described in PTL has been presented.
FIGS. 10A and 10B illustrate a configuration of an example of the related art described in PTL. An elastic member is provided so as to be connected to an action unit having a plate shape, and a magnetic-flux generating source 102 is embedded in the elastic member. Four magnetoelectric transducers 101 are disposed so as to oppose the magnetization directions of the magnetic-flux generating source 102. When a force is applied to the action unit, the magnetic-flux generating source 102 is displaced by elastic deformation of the elastic member. Changes in magnetic flux density that are generated by the displacement are detected by the magnetoelectric transducers 101. Accordingly, force components acting along three axis directions, i.e., the X-axis and Y-axis directions along which the magnetic-flux generating source 102 is displaced in the horizontal direction with respect to a plane including the magnetoelectric transducers 101 and the Z-axis direction along which the magnetic-flux generating source 102 is displaced in the vertical direction with respect to the plane, can be detected.
However, in a magnetic force sensor that is typified by the sensor described in PTL given above, a magnetic field that is generated in a region including positions of the magnetoelectric transducers 101 has gradients in both the horizontal and vertical directions. The magnetic field changes in accordance with a direction in which the action unit is displaced, and the changes in the magnetic field are detected utilizing the gradients of the magnetic field, thereby detecting forces. For this reason, in some cases, interference from the other axis components becomes a problem, in which outputs along a measurement target axis are influenced by outputs along the other axes.
For example, a problem of interference from the other axis components occurs, in which, regardless of reception of an external force resulting in displacement only in the horizontal direction, changes in outputs that should be generated in a case of displacement in the vertical direction also appear because of an influence of the gradients.
The present invention has been made in order to solve the above-described problems, and provides a magnetic force sensor that reduces interference from the other axis components which occurs between horizontal-direction components and vertical-direction components.